fish is good and we should all eat loads of it – we live on an island after all!
however the problem with farmed salmon is twofold, first that they are feeding the salmon on wild caught fish and there is a drop in efficiency. without bothering to search for actual figures, the idea is that 10kg of wild fish like sardines go into 1 kg of salmon. the sardines are better for you then salmon so its a waste. second, the fish farms often (not always) have a detrimental effect on the area around them – slamon dont tend to congregate in such numbers and the waste and parasites they give off cause damage to wild fish staocks local to them.
the other problem is that salmon is a top predator (unlike cows in the farmed beef analogy above) this means that they are accumulating all the toxins from the prey they are eating (heavy metals etc) which you are then eating, and also accumulating over your lifetime. heavy metals cause problems in the brain later in life (dementia etc) – something heavily on the rise
ever wondered why we dont eat land predators?